They're great bikes mate, stacks of power and excellent braking and handling, you won't be disappointed! The clutches rattle on all of them, and you can get them rebuilt but it's not normally required, (unless the bike has been an ex-racer) and synching the carbs will reduce it somewhat too.
Suzuki basically copied Kawasaki's Z1 to build the GS1000, but they made a much better mousetrap. While the Zi looked beautiful, Kawasaki were not good frame builders, so they were known then as "widow-makers".
Suzuki, on the other hand had more experience with racing, so made a really strong, but reasonably light frame, and when it was released, it was described as "Possibly the best bike ever built", which is one hell of a compliment!
I've got a 1981 GS1000S "Wes Cooley Replica", and a 1979 GS750, plus a couple of parts bikes. I'm thinking about putting the parts bikes back together, as these bikes are so "bullet proof", you don't need a parts bike! Cheers, Terry.